1. Field of the Invention
This invention relates to an electric flash which carries out a slave flash.
Further, this invention relates to a connector which connects an accessory shoe of a camera and an electric flash to allow the electric flash to carry out the slave flash.
2. Description of the Related Art
Conventionally, multiple flash photography using the slave flash has been commonly known.
FIG. 10 is a view showing the multiple flash photography.
In FIG. 10, a camera 92 is arranged with a predetermined shooting distance from a subject 91. A master-side flash 93 is connected to the camera 92.
Meanwhile, an electric flash 94 on a slave side is independently arranged at a position for additionally illuminating the subject 91. An optical detecting part 95 for detecting light of the master-side flash 93 is provided at the electric flash 94 on the slave side.
FIG. 11 is a view explaining the operation of the above slave flash.
First, the master-side flash 93 starts flash light emission according to the control of the camera 92. The optical detecting part 95 receives the flash light.
When a received light quantity exceeds a detection level of a flash start (LA shown in FIG. 11), the optical detecting part 95 detects a flash start of the master-side flash 93. The electric flash 94 on the slave side starts the flash light emission in synchronization with the detection timing.
Meanwhile, the camera 92 measures a reflected light quantity of a film (or an imaging element). When the camera 92 determines that an exposure reaches an adequate level based on the reflected light quantity, it stops the flash of the master-side flash 93. As a result of this, a flash quantity of the master-side flash 93 attenuates quickly and the received light quantity of the optical detecting part 95 decreases.
When the received light quantity falls below a detection level of a flash stop (LB shown in FIG. 11), the optical detecting part 95 detects a flash stop of the master-side flash 93. The electric flash 94 on the slave side stops the flash light emission in synchronization with the detection timing.
Incidentally, it is assumed that the master-side flash 93 and the electric flash 94 are arranged close to each other with the objective of increasing the flash quantity (the so-called guide number) and the like. When these are arranged closely like the above, there is a high possibility that the optical detecting part 95 obstructs a light path of the master-side flash 93, which may cause a disadvantage such as a shadow cast over the subject.
Further, the aforesaid electric flash 94 detects flash start of the master-side flash 93 when the received light quantity reaches the detection level LA. Hence, the flash start of the slave flash falls behind the flash start of the master-side flash 93. This delay of the slave flash causes a change in an illumination ratio between the master side and the slave side, as flash time shortens.
Moreover, there is a possibility that the flash of its own is detected by the aforesaid electric flash 94. In this case, an optical detection signal of the optical detecting part 95 is likely to be saturated, which may cause disadvantages such as the delay of the detecting operation of the flash stop, and the impossibility of detecting the flash stop.
Furthermore, there is a possibility that the aforesaid electric flash 94 detects light from the outside and flashes erroneously. In this case, it is necessary to wait for a while until the electric flash 94 is ready for the next flash, which may cause a disadvantage of missing important photo opportunities or the like.
In view of the above disadvantages, it is an object of the present invention to provide an electric flash which is disposed close to a master-side flash and able to carry out a good slave flash.
Further, it is another object of the present invention to realize a slave flash with the same principle as the electric flash of the present invention by contriving a connector for connecting an accessory shoe of a camera with a conventional electric flash in order to.
Hereinafter, the present invention will be explained.
(1) The electric flash according to the present invention is an electric flash disposed for use close to a master-side flash whose flashing is controlled by a camera, comprising a flash source for emitting flash light to illuminate a subject, a trigger noise detecting part for detecting trigger noise generated from the master-side flash, and a flash control part for controlling the flashing of the flash source in synchronization with the trigger noise detected by the trigger noise detecting part.
Generally, the master-side flash emits the trigger noise to the outside under the flash control (flash start, for example) of the master-side flash. This kind of trigger noise is weak and its radial direction is wide. Hence, it is impossible to detect the trigger noise at positions distant from the master-side flash because it is buried in surrounding electromagnetic waves.
Meanwhile, the electric flash according to the present invention is disposed for use close to the master-side flash. Therefore, the trigger noise detecting part included therein can detect the trigger noise excellently. The flash control part controls the flash source in synchronization with detection result of the trigger noise, and carries out the slave flash.
As described above, unlike the conventional art the electric flash according to the present invention does not need to receive the light of the master-side flash. Therefore, the electric flash need not be disposed unnecessarily in a light path of the master-side flash so that it is unlikely to occur that the light of the master-side flash is erroneously interrupted.
Moreover, the trigger noise is generated at the time of controlling the flashing of the master-side flash. Therefore, it is easy to detect the flash start more quickly than the conventional example which detects the start after the flash light emission is actually started. Hence, according to the present invention, it is possible to easily realize the electric flash which carries out the slave flash almost simultaneously with the flash light emission of the master-side flash.
(2) According to another aspect of the present invention, the flash control part of the above electric flash (1) stops the flashing of the flash source in synchronization with the trigger noise detected by the trigger noise detecting part after the start of the flashing of the flash source.
It is determined that the trigger noise detected after the start of the slave flash as described above is caused by the flash stop of the master-side flash. Hence, the flash control part stops the slave flash in synchronization with the trigger noise.
This operation enables the slave flash to be stopped in accordance with the timing of the flash stop of the master-side flash.
(3) According to still another aspect of the present invention, the above electric flash (1) further comprises a detection invalid part for invalidating the detection of the trigger noise in synchronization with the control timing of the flashing of the flash control part, and preventing a malfunction of the flash control part due to spontaneous noise.
In the conventional example, the malfunction is caused by receiving the slave flash of its own. Similarly, it is also concerned that the malfunction occurs due to spontaneous noise (trigger noise generated from the electric flash itself) in the present invention.
However, the trigger noise on the master side and the trigger noise on the slave side are deviated in terms of time, and hence it is possible to distinguish the source of the trigger noise on a time basis.
The detection invalid part with the above structure invalidates the detection of the noise (that is, the spontaneous noise) according to the control timing of the slave flash. Thereby, it is possible to remedy a defect that the slave flash operation is disturbed by the spontaneous noise.
(4) According to yet another aspect of the present invention, the flash control part of the above-described electric flash (1) has a function of accepting a flash control signal supplied from the camera. Further, when the supply of the flash control signal precedes the detection of the trigger noise, the flash control part inhibits the flash control by the trigger noise and controls the flashing by the flash control signal.
There are in general two types of camera having a built-in flash: one outputs the flash control signal to the outside under the condition where the built-in flash is able to flash, and the other does not output the signal.
Therefore, when performing additional illumination by an external electric flash, a user needs to determine whether he/she uses the flash control signal of the camera or carries out the slave flash, as necessary. The determination has nothing to do with artistic expression in shooting, and causes some trouble.
However, according to the present invention, when the flash control signal is supplied prior to the detection of the trigger noise, the flash control under the flash control signal is carried out with priority.
Moreover, when the flash control signal is not supplied, the slave flash based on the detection of the trigger noise is carried out.
By this operation, the flash control signal and the detection of the trigger noise do not compete with each other, and the normal flash operation of the electric flash is secured irreverent of the type of camera in the present invention. Thus, the troublesome determination is unnecessary and the easy-to-use electric flash is realized.
(5) According to still another aspect of the present invention, the master-side flash is built into the camera in the above electric flash (1). The electric flash further comprises a leg part attached to an accessory shoe of the camera being in a state that the master-side flash is able to flash (for example, the flash part is in a pop-up state).
Using the leg part with the above structure allows the electric flash to be easily disposed close to the master-side flash which is able to flash.
(6) According to yet another aspect of the present invention, the above electric flash (5) further comprises a determination part for determining whether the master-side flash is able to flash, and a malfunction preventing part for inhibiting the flash control by the trigger noise when the determination part determines that the master-side flash is not able to flash.
In the above structure, when the determination part detects that the master-side flash is unable to flash, the malfunction preventing part inhibits the flash control by the trigger noise. This decreases possibility in carrying out the slave flash due to an erroneous detection of extraneous noise as the trigger noise.
(7) According to still another aspect of the present invention, in the trigger noise detecting part of the above electric flash (1) at least one of its detection sensitivity, detection frequency, and detection waveform is/are limited to detect not an electromagnetic wave from a distance (other than the master-side flash), but the trigger noise from the master-side flash disposed close thereto.
In the above structure, at least one of the detection sensitivity, detection frequency, and the detection waveform is limited so that the trigger noise and the electromagnetic wave from a distance are discriminated from each other. This lessens possibility in erroneously carrying out the slave flash due to the electromagnetic wave from a distance.
(8) The connector according to the present invention is a connector for connecting an accessory shoe of a camera with an electric flash, comprising a trigger noise detecting part provided on a side connected to the accessory shoe, for detecting trigger noise generated from a master-side flash built into the camera, and a signal output part for outputting a flash control signal for controlling flashing to the electric flash, in synchronization with the trigger noise detected by the trigger noise detecting part.
The connector with the above structure detects the trigger noise of the master-side flash at a connecting part of the accessory shoe, and outputs the flash control signal to the electric flash according to the trigger noise.
Therefore, by using the connector, it is possible to use the conventional electric flash as it is and easily carry out the slave flash of trigger noise detection type.
Incidentally, it is preferable to add an element described in one of the above (2) to (7) to the connector as structured above. In this case, the conventional electric flash is employed to easily perform xe2x80x9cthe slave flash of the trigger noise detection typexe2x80x9d according to any one of the above-described (2) to (7).